Anterior floor-reaction type ankle-foot orthosis

ABSTRACT

An interior moulded floor-reaction (FR) ankle-foot (AFO) (10) is described which has a fixed ankle angle and a detachable heel wedge (16) which allows the vertical alignment of the brace to be adjusted. The anterior leg portion (12a) has an elastic calf strap (14) for controlling plantar flexion. The AFO is moulded in a single piece of plastic with the leg portion (12a) being integral with the foot portion (12b) and the elastic strap (14 ) passes around the back of the calf. The FR AFO fits inside the patient&#39;s shoe.

TITLE OF THE INVENTION

The present invention relates to floor-reaction type ankle-footorthosis.

BACKGROUND OF THE INVENTION

An anterior floor-reaction orthosis (AFRO) is a brace that prevents theankle joint from dorsiflexing. In the case of a paralysed limb, withoutany brace, the ground reaction vector passes through the ankle jointbecause no torque can be transmitted. However, with an AFRO, the base ofthe ground reaction vector can be moved forward to the metatarsal regionof the foot as shown in FIG. 1a. In this position the ground reactionvector acts ahead of the anatomical knee joint axis and thus stabilisesthe knee in extension without muscular action.

Traditionally, a paralysed leg is braced using a knee-ankle-footorthosis (KAFO) that incorporates a mechanically lockable jointpositioned at the side of the anatomical knee. In contrast, the anteriorfloor-reaction orthosis (AFRO) principle may be used to stabilise theparalysed leg without physically locking the knee in extension. This hasthe major advantage that during the swing phase of walking the knee canflex to gain ground clearance. In addition, this provides improvedcosmesis and reduces weight and cumbrance. However, the AFRO onlystabilises the knee on the condition that the ground reaction vector isahead of the knee axis as shown in FIG. 1a. If the ground reactionvector should shift behind the knee as shown in FIG. 1b, then the kneewould buckle and the leg would collapse if there were no knee extensormuscle action. Thus, the AFRO is only used or prescribed when thepatient has sufficient control of his knee extensor musculature to avoidcollapse in these situations. Alternatively, paralysed muscles may beelectrically activated in response to such an incident as disclosed inU.S. Pat. No. 5,121,747.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improvedfloor-reaction orthosis which obviates or mitigates at least one of theaforementioned disadvantages.

This is achieved by providing a moulded plastic orthosis shell formed tobe in close approximation to the anatomical limb. The leg portion of theplastic shell includes an elastic calf strap for controllingplantarflexion and a detachable heel wedge is provided which allows thevertical alignment of the brace to be adjusted. The improved foot-ankleorthosis fits inside the patient's shoe.

In one arrangement the floor-reaction orthosis is moulded in a singlepiece of plastic with the leg portion being integral with foot portionand the elastic strap is fastened to the top of the leg portion andpasses round the back of the calf. The brace is fabricated such that thefoot portion is made in one angled position which is typically 10°plantarflexion. This allows various heel wedges to be inserted beneaththe heel to allow correct vertical alignment of the subject in the braceso that the correct ground reaction vector position is achieved. Thispermits accommodation of variations presented by different shoe heelheights.

The device is straightforward to fabricate and uses a thermoformedplastic sheet or fibre composite laminate which is made by thermoformingthe plastic sheet over a plaster of paris mould of the patient's leg.

According to one aspect of the present invention, there is provided afloor-reaction orthosis comprising a below-knee moulded orthosis shellproportioned and dimensioned to be in close proximity to the anatomicallimbs, said shell having a leg portion and a foot portion, said legportion fitting over the anterior surface of the limb, and the footportion being coupled to the leg portion to wrap around the foot, saidleg portion having an elastic strap coupled thereto for fitting aroundthe calf of the limb, said shell being moulded for a single ankleposition of plantarflexion, said foot portion being adapted to receiveseparate heel means for providing, in use, correct vertical alignment ofthe subject in the orthosis whereby the correct ground reaction vectorposition is achieved.

The leg and foot portion are integrally moulded and fabrication isachieved by thermoforming a plastic sheet over a plaster of paris castof the patient's leg. The orthosis may be moulded in a specific angle ofplantarflexion depending on the requirements of a particular patient andthe elastic strap can be fixed to the anterior surface of the orthosisby a number of ways, for example, slots may be moulded in the anteriorsurface and the strap passed therethrough or else the strap may besecured to the orthosis by fastening means, such as rivets and the like.

According to another aspect of the present invention there is provided afloor-reaction orthosis comprising a moulded anterior limb portionintegral with a foot portion, the limb portion having an elastic strapcoupled thereto for fitting around the calf of the limb, and the mouldedportion being mould to a specific angle of plantarflexion foraccommodating heel wedges to provide correct vertical alignment of thesubject in the orthosis.

These and other aspects of the present invention will become apparentfrom the following description when taken in combination with theaccompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b are views showing the ground reaction vector;

FIG. 2 is a perspective view of an embodiment of a floor-reactionorthosis (FRO) in accordance with the present invention;

FIG. 3 is a side view of a limb fitted with the floor-reaction orthosisshown in FIG. 2 with an adjustable heel wedge;

FIGS. 4a and 4b depict how the control of plantarflexion is achievedwith the FRO by means of the elastic strap.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference is first made to FIG. 2 of the drawings which depicts afloor-reaction orthosis generally indicated by reference numeral 10which consists of a plastic moulded shell 12 which is formed to fit thefront of the calf and the foot of the patient and which has an elasticstrap 14 attached thereto for securing the anterior shell portion 12a tothe patient's leg. The plastic shell is fabricated from thermoformedplastic sheet or fibre composite laminates by thermoforming the sheetover a plaster of paris mould of the patient's leg. As best seen in FIG.3, the orthosis shell 12 is fabricated in a single angle position suchthat when fitted to-the-subject as shown in FIG. 3, there is a spacebetween the heel of the subject and the floor. This allows a plasticheel wedge 16 to be inserted at the heel to allow the correct verticalalignment of the subject in the brace so that the correct groundreaction vector (GRV) position is achieved; this means that the GRVpasses in front of the knee as shown in FIG. 3. The angle of fabricationis typically 10° of plantarflexion and can accommodate variationspresented by different shoe heel heights.

Reference is now made to FIGS. 4a and 4b of the drawings which depictsthe control of plantarflexion by means of the elastic strap 14. Theelastic strap 14 stretches to provide plantarflexing control during thefoot contact to foot-flat phase of early stance phase as indicated inFIGS. 4a and 4b respectively. The traditional ankle-foot orthosisimmobilises plantarflexion and produces an unnatural gait similar towalking in rigid boots, for example, ski boots. With the presentfloor-reaction orthosis natural gait is facilitated because a naturalrollover is provided similar to normal walking. At heel contact as shownin FIG. 4a, the heel portion 16 contacts the ground first and as forwardmovement occurs the orthosis leads the leg by virtue of the elasticstrap 14 mimicing natural rollover and as the forward motion of thesubject continues, the orthosis is retained on the leg as shown in FIG.3.

The embodiment hereinbefore described provides a number of advantagesover the prior art devices. Because the orthosis is moulded in a singlepiece, ankle joint components are not required and it is straightforwardto fabricate the shell using thermoformed plastic sheet or fibrecomposite laminates. In addition, with the new floor-reaction orthosisfor a given thickness of plastic material, the new shell is stiffer inresisting dorsiflexion. This allows thinner section materials to be usedwhich in turn allows a shoe size closer to, or the same as, thepatient's to be used. In a traditional ankle-foot orthosis it is usuallynecessary to go up at least one shoe size to accommodate the orthosisthereby adding unnecessary weight and foot length that adversely affectsground clearance during swing phase. With present orthosis no extra footlength is required facilitating natural rollover and providing cosmesiswhich is also important.

The elastic strap provides plantarflexion control during the footcontact to foot-flat phase of early stance phase as hereinbeforedescribed whereas the traditional ankle-foot orthosis immobilisesplantarflexion and produces an unnatural gait similar to walking inrigid boots. The plastic heel wedge allows the correct verticalalignment of the subject in the brace so that the correct groundreaction vector position is achieved. This allows the brace to befabricated with one ankle position which is typically 10°plantarflexion, but accommodates variations presented by the differentshoe heel heights.

It will also be understood that the floor-reaction orthosis hereinbeforedescribed could be used in combination with a functional electricalstimulation system, such as disclosed in U.S. Pat. No. 5,121,747 orcould be used by itself.

I claim:
 1. A floor-reaction orthosis comprising a below-knee mouldedanterior floor-reaction orthosis shell proportioned and dimensioned tobe in close proximity to the anatomical limbs, said shell having a rigidleg portion and a foot portion, said leg portion fitting over theanterior surface of the limb and adapted to permit the limb to pull awayfrom being in contact with the leg portion when in a standing state, andthe foot portion being coupled to the leg portion adapted to wrap aroundthe foot, said leg portion having an elastic strap coupled theretoadapted to fit around the calf of the limb, said shell being moulded fora single ankle position of plantarflexion; and a separate heel means onsaid foot portion for providing correct vertical alignment of thesubject in orthosis whereby a predetermined ground reaction vectorposition is achieved.
 2. A floor-reaction orthosis as claimed in claim 1wherein the orthosis is moulded in a specific angle of plantarflexion.3. A floor-reaction orthosis as claimed in claim 2 wherein the specificangle is about 10° plantarflexion.
 4. A floor-reaction orthosis asclaimed in claim 1 wherein said separate heel means is a wedge-shapedelement.
 5. A floor-reaction orthosis as claimed in any preceding claimfurther comprising slots are located in an anterior surface of theorthosis and wherein said elastic strap passes through the slots.
 6. Afloor-reaction orthosis as claimed in claim 1 wherein the elastic strapis secured to an anterior surface of the orthosis by rivets.
 7. Afloor-reaction orthosis comprising an anterior floor reaction orthosiswith a moulded anterior limb portion integral with a foot portionwherein the limb portion is adapted to permit a limb to pull away in acontrolled manner from being in contact with the limb portion in astanding state, the limb portion having an elastic strap coupled theretofor fitting around the calf of the limb, and the moulded portion beingmoulded to a specific angle of plantarflexion for accommodating heelwedges to provide correct vertical alignment of the subject in theorthosis; and a heel wedge attached to said foot portion.
 8. An orthosiscomprising:an anterior floor-reaction orthosis shell with a foot portionand an anterior limb surface portion; a posterior limb surface supportmeans for holding a limb against an inside surface of said anterior limbportion during a limb swing state and for permitting said limb to pullaway in a controlled manner from said interior surface of said anteriorlimb portion during a stance state and a vertical alignment deviceattached to a bottom heel portion of said foot portion.
 9. An orthosisas claimed in claim 8 wherein said posterior limb surface support meanscomprises an elastic band.
 10. An orthosis as claimed in claim 8 whereinsaid vertical alignment device comprises a wedge-shaped heel.